Free disk space
Reduce the size of backups and the time to create them by removing unnecessary files
Maintain privacy
Improve system performance (by vacuuming the Firefox database, for example)
Prepare whole disk images for compression (common for "ghost" backups and virtual machines) by wiping free disk space

Cleaners

BleachBit includes a growing list of cleaners. Typically each cleaner represents an application such as Firefox or Internet Explorer. Within each cleaner, BleachBit gives options covering components that can be cleaned such as cache, cookies, and log files. Each option is given a description to help you make good decisions.